Airfoil



J. GITZ ET AL Sept. 27, 1949.

AIRFOIL 3 Sheets-Sheet? Filed May 1,v 1945 INVENTORJ. do/m G/'f ,fl/fred Z. aya/fan.

ATTOBNEY sept. 27, i949. J, GlTz ETAL 2,483,134

A AIRFOIL Filed May l, 1945 3 Sheets-Sheet 3 ATTORNEY Patented Sept. 27,' 1949 Farmingdale, N, Y., assignors to Republic Aviation- Corporation, Farmingdale, N. Y., a corporationof Delaware Application May 1,1945, Serial No. 591,332

Thisl invention relates generally to aircraft' structures and more particularly proposes aconst'ruction having for its object such simplification of' metallic airf'oils that the cost of manufacturing and assembling the components thereof is reduced without-sacrificing strength or utility.

Airfoil as used herein is to include all iixed airfoils such as wings, stabilizers, fins, etc.,.as well afs-all' movable control surfaces, such as ailerons, flaps, elevators, rudders andthe like.

In. conventionalpractioe, a metallic airfoil has consisted'of a basic framework or skeleton, usually fabricated of several. capped spars to which are securedribs and other trussing or stiifening meinber's, and a sheet metaicovering or skin usually in' the form of a series of relatively small panels or skinisections overlapped at adjoining edges and securedto said framework.V Thispricr practice is' relatively slow, expensive and disadvantageous in that' it' requires the fabrication and assembly of. many separate parts, fittings, cap: angles,` stringers, etc., the manufacturing, finishing and machining'of which is costly andtime consuming', andi a-lso requires complex riveting and assemabling operations occasioned by the numerous'v ele;- ments or parts making up'th airfoil and by the relatively small skin panels or sections many of which are rectangular in shape and require riveting or'fastening at all four edges.

The present construction contemplates the use ci formed sheet metal for the majority, if not all, of the components thereof, and the arrangement and correlation thereof into a' simple frame wrapped: or'enveloped in one or more. skin sections or panels,` each developed from a single stiened sheet or' section of metalzbent upon'vit# self to have" its edge portions adjacent to or at the trailing edge of the airfoil.

Basically this -airfoil greatly reduces the num'- b'er of frame elementsenflployed and'simplies the production of each of such elements -byemploying standard sheet metal forming technique, made possi-ble by tlie structure of the several frame elementsk and their cooperation with eachother and with the enveloping, stienedskin. By its simplification audits reduction in the number of elementsy embodied in the airioil, the instant invenftion substantially reduces timeV and expense involved in fabrication andiv assembly, Vthereby attaining material reductions in the overall cost-s of` airplane production.

With. the. above' and other objects in view, as will bei apparent, this. invention consists inthe construction', combination# and arrangement oi parts al-lias hereinafter more lul-lydescribed,

9 Claims. (C1. 244-123) 2 claimed' and illustrated in the accompanyingdrawings, wherein:

Fig. 1. is a plan View of an airfoil here illus# trated'asa wing, constructed in accordance With the present invention:

Fig. 2 isa corresponding plan view of the frame or skeleton of the airfoil or wing of the instant invention exposed by the removal ofthe skin:

Fig. 3 is a transverse section taken along line 3--3 of Fig. 1 to be read in conjunction with either Fig; 4' or Fig. 5 along lines A-A to disclose the complete sectional profile of the airfoil or wing at' the points indicated for they sections of Figs. fl-and 5:

Fig; 4 is a transverse section taken along lines Iii-i of Fig. 1 to show the trailing edge construction and is to be joined with Fig. 3 along line A-A toA establish the complete airfoil sectional profile between'lthe aileron and the root end thereof:

Fig. 5 is asimilar section taken along line 5 5; ofFig. 1 to illustrate the aileron construction and is to be joined with Fig. 3 along line A-A to disclose-the complete airioil prole section through the aileron:

Fig. 6 isv afront elevation of the wing with parts of the skin broken away and in section to disclosed the skin structure, the interior frame or skeleton and the cooperation between the overlapped adjacent edges of the panels or sections of theskin:

Fig. 7 isY a horizontal enlarged fragmentary section taken along line 'ih-'l of Fig. 3 to illustrate the construction of the root end-piece or rib of the airfo'il and its cooperation with the several spars: and

Fig. 8l is an enlarged fragmentary vertical section taken along line 8'8 of Fig. 3 to show the cooperation between the spar and the inboard or root end-piece or rib'.

The present invention resides in an airfoil structure and the technique by which it may be produced and-assembled, and is applicable to substantially all types of stationary or movable airfoils` and controlv surfaces. For illustrative purposes itY is shown and described as applied to a wingand coacting aileron, but it will be apparent that, with only minor modifications and changes necessitated by the character and size of the' airfoil` o'r control surface substantially the same structure can be employed for rudders, elevators, naps', stabilizers, ns or any other airioil orY control surface.

Reference being had more particularly to the drawings, the basic frame or skeleton structure ofv the airfoilV consists of two or more spars Wand 3 I', the outer spars I8 being situated adjacent the leading and trailing edges of the airfoil, while the intermediate spar or spars Eil' are located parallel to and between the outer spars It. These spars Ill and Ill' are identical in construction except where the inboard ends of the outer spars Hl may be used as fittings to attach or mount the wing or airfoil, as will be described. IThe intermediate spar or spars iii are provided for additional strength and rigidity and unless required may be eliminated.

C'oacting with and traversing the ends of the spars I0 and I9 are the end-pieces comprising the inboard rib II and the outboard rib I2. No intermediate ribs between the extremities of the airfoil are contemplated though it is of course possible to incorporate them in the airfoil construction following the teachings hereof. The ribs II and I2 not only serve as structural parts of the frame or skeleton of the airfoil but also are end-pieces closing the extremities thereof. Parallel to the ribs or end-pieces I2 and medially therebetween is situated a stub rib-section I 3 which, in combination with the outboard rib I2, defines a space at the trailing edge of the ail-foil or wing in which the aileron is situated. This stub rib-section I3 is constructed and made, except as to size, identically with the ribs II and I2 and also generally like the spars IIl-I il.

The aileron mounted in the space deined by and between the outboard rib I2 and the stub ribsection I3 has a frame or skeleton comprising three ribs I4 spaced one from the other spanwise of the wing, the outer or end ribs I4 being respectively situated adjacent the rib I2 and the stub rib-section I3 while the other id is located centrally between said outer or end ribs. The frames thus described are the entire internal frame structure of the airfoil and of the aileron and the components thereof are individually made of sheet metal by using standard sheet metal techniques as will be hereinafter set forth.

Each of the spars I-I' is constructed of sheet metal and comprises a relatively flat web It" of the required length, having transversely bent flanges I5 at both of its longitudinal edges thereby imparting U-section to the spars. Between its ends and between the fianges I5 the web of each spar is pierced by a series of lightening holes Iii, the edges of which are bent outwardly at an angle to the body of the web to create the obliquely positioned, circular or conical flanges II. Thus each spar is provided with a longitudinal flange at each of its longitudinal edges and with a series of annular conical flanges Il intermediate of its edges and occurring periodically throughout its entire length, the flanges I5 projecting from one face of the web lil" in opposition to the conical flanges Il which project from the opposite face of the web. The flanges I5 at the longitudinal edges of the spar not only provide a means for mounting and securing the skin to the spars, as will be hereinafter more fully described, but also strengthens the spar through its entire length. The lightening holes I6 not only reduce the weight of the spar but the flanges I'I thereof add stiffness and strength thereto.

Regardless of the number of intermediate spars IIJ' employed, each is provided with a lateral ange I 8 at each of its ends, to rest flush against and be secured to the inner surfaces of the ribs or end-sections II and I2 as will be hereinafter described. The flanges I8 also add strength and stiffness to the spar IB'. Each of the outer spars Iii, at the point where it abuts or adjoins the outboard rib or end section I2, is also provided with a transverse end flange I9, similar to the end iianges I8 of the intermediate spar I0', to rest flush against the inner face of the outboard rib or end section I2 and be there secured as will be hereinafter more fully described. As in the case of the intermediate rib I0', the end ange I9 of the outer spars I0, in addition to providing means for attaching the spars I0 to the rib or end-section I2, also strengthens and stiffens them.

The end-sections or ribs II-I2 of the airfoil structure are substantially identical and each comprises a web 23 of shape and form to define the outline or contour of the ultimate airfoil, having a continuous lateral flange or lip 23 formed integrally at its edge. The web 23 is pierced by a series of lightening holes 2I each surrounded -by an annular, conical flange 22. As shown in Fig. 7, the flanges 22 surrounding the lightening holes 2| project from one face of the web 23 while the continuous, integral flange 2B at the edge of the web projects from the opposite face thereof. The continuous flange 2d of each rib or end-section I II2 and the conical anges 22 surrounding the lightening holes 2l combine to strengthen and stiien not only the rib or endsection per se but also impart strength and rigidity to the entire airfoil structure.

In assembly the spars I Il-I are positioned parallel one to the other with the end-sections or ribs II-IZ so traversing or crossing the opposed ends thereof that their respective flanges 2li project outwardly at the ends of the airfoil and away from the spars III-|02 When so situated the end flange I8 of each intermediate spar and the end flanges I9 of the forward and aft spars Iii-Iii all rest flush against the inner face of the web 23 of the outboard rib or end section I2, where they are xedly secured by rivets 23' or other suitable fastening means. As will be pointed out, the inner end-portions of the forward and aft spars lil may pass through or may terminate at the inboard or root end-section or rib II and in either event they are rigidly and securely attached to the web 23 of said end-section or rib II Thus the main skeleton or frame of the airfoil consists of the spars IIl and, if desired, one or more intermediate spars I0', all rigidly secured at their ends to the end-sections or ribs l I-IZ whereby a rigid, stiff frame structure is produced having the flanges 2U of the end-sections or ribs II-IZ projecting outwardly of the frame or skeleton structure so constituted.

As shown herein by way of example the iniboard ends of outer spars I0 pass through slots 24 formed in the web 23 of the inboard end-section or rib II in alignment with the webs I0 yof the spars I0. The material from the slot 24 is only severed from the body of the web 23 along three sides of the slot so that it may be bent angularly to the web to create a lip 25 resting ush against one face of the web I0" of the spar I0. An angle plate 26 approximately coextensve with the width of webs I8-23 is so attached or secured to the web 23 of the end-section or rib II by the rivets or other fastening means 2l piercing the plate 26 and the web 23, that one 0f its -arms 28 rests flush against the web I 0" of the spar I0 in opposition to the lip 25. Rivets or other suitable fastening means 29 pierce the arm 28 of the angle plate 26, the web of the spar I 0" .and the lip 25 thereby rigidly securing these elements into a solid, unitary structure. Vihile the :formation of the slot 24 in t-he web 23 of the inboard endsection or rib II may possibly tend to weaken the rib or end-section ,at that point, the angle plate 2B secured to the web 23 vof' the end-section I-I and to the web l" of the spar IIland as well as totheli-p 25l overcomes this weakness and results ina unitary structure as strong, ifnot stronger, than the web 23 would be Without said; opening or slot,

The web I0" of each spar i3 passes through the opening or slot 24 in the web 23 of the end'- section or ri'b IIv to terminate beyond the limits of the anges 20 of said rib or end-section, asillustrated in Figs. 2 and 7. In order to clear the ilange 2B of the end-section II on both sides of the spar, the anges I at the opposite edges of the spar are cut away as at 30. 'Ilhus the flanges V2li of the end-section or rib IIA are lbridged or spanned by being received in the recesses 30 and the normal construction of the `spar continues or is resumed in the porti-cn 3| projecting beyond said end piece or rib. The projecting portion 3| of the spar I0 constitutes, if desired, a wing hinge tting. An alternate structure readily suggests itself. To that end the spars I0 may terminate at the inner face of the web 23 of the end-section or rib I-I to be there securedl by laterally formed end flanges exactly as the corresponding end of the intermediate spar I0' is secured to the web 23, in which event a wing hinge fitting 3l may' be secured sto the outer face of web 23 the rib or end-section II in alignment -with the web IIIA of the spar Iii byl rivets or other suit-able fastening means. instead of having the spar I0 projecting or passing through the web 23 of the rib II, it may end at and be secured to one Iface ofthe web 2,3 of the rib while 4a hinge fitting 3II is secured' to the opposite or outer face of said web in alignment therewith.

'Bhe stub'rib-section I3 agrees ingeneral shape, contour and length with those portions of the ribs or end-sections II-I2 which lie aft of the spar Il!k situated adjacent the trailing edge of the airfoil structure. This stub section I3 comprises a web I3 having a laterally extending flange 13b at its louter edges simil-ar to the flanges 20 `of the end-sections Ior ribs I I-I2. At its inner end the web I3 of the stub sectionV I3 is provided with a laterally disposed ilange or lip I3 which rests flush against the outer surface of the web I0" of the aft spar Ill to lie secured thereto by rivets or other suitable fastening means I3a. In this manner the stub rib-section `I3 lies lparallel t0 and is coextensive Ywith the projecting end portions of the ribs or end pieces Il-I2 located aft of the rear spar It. The continuous l-ateral flange |312', at the edge of the web I 3 of the stub section I3 extends toward the end sectionor rib I2 and hence outwardly of that part of the trailing edge of the wing situated between said stub section and the inboard rib or end-section II.

' All of the elements hereinbefore described are formed from sheet metal with the lightening holes stamped therein with the conical anges pressed tov project outwardly from one face of the webs thereof and integral lateral flanges formed at the edges 4of the webs to project from the face thereof 'opposed to the conicallanges. The forming of these elements follows the conventional Vlletal shaping technique in that each component is originally a flat metal sheet punched and formed in the conventional manner. No extensive or expensive machining zor finishing operations lof these formed sheet meta1 parts are required and, as will be seen, the assembly thereof in combination withV theV skin ofthe meta1 airfoil 6l merely entailsv` the. -use of: standard; fastening means, such as rivets, :torcomplete theairfoiluns der most circumstances. f f

Over the frame thus. formed: off the vspal's I-.f-Iif and theI end-sections. or ribs. IIN-I2 is wrapped the. skin of. the airfoil which may. be in the forni. of one or.` more. sections or; panelsy 3.2.. This skin originates from. a .flat sheet of; met-al havingv the ribs 33V formed therein upon Opposite sides. of a. central'. zone 34. These ribs 33.,A shown in Fis.. 3, extend' in opposite directions on eacnside of the Smooth central zone .34 toward the opposed edges of the sheet from which the skin panel is made. The sheet thus formed iS then bent toenvelope or wrap the frame so that the relatively smooth centralzone 34. constitutes the leading edge of the airfoil. while the Sheet upon each side :of said centralzone comprises the upper and lower` surfaces of the airfoil with the edges of the sheet at or adjacent the tr-ailingedge of the airfoi-l. When the sheet isv thus bent. 0.1 wrapped. around the frame the flat portions. 35 thereof dened Eby the beads 33 rest flush against the laterally disposed anges I5-2I) respectively on the end sections or ribs Ll-IZ and spars Iii-IB. Rivets 36 are then passed through the portions 3 5 of the panel and the flanges I5-2IJ :at spaced intervalsA to secure the skinA rigidly to the fra-me at all points where the portions 30 of the panelV 32-v contact and' rest iiush on said flanges. Since the anges 20 and |31) respectively-of the end sections or ribs I-I-I2- and the Stub section I3y and thev flanges I5 of the aft spar I project -outwardly of the airfoil structure, rivets may easily :be inserted in place thenA :and headed without resorting to blind riveting.

In the adaptationy ofV the invention shown herein, four sections or panels 32 of the skin are employedl though it is tobe understood: thatone or more panels. 32.' may be employed. to wrap. the internal. frame with equal facility. When more than one panel 32. is employed the adjoining edges ofthe panels overlapas shown in. Fig. 5 and are secured one to the other by the rivets 31.

in, viz: adapted to a wing, the aileron spaces Y defined by. the Stub` rib-seotion I3` and the D130- jecting aft end of the end section or rib t2. necessitates shorter upper and lower skin sur,- faces. Therefore the two inboard skin panels 32 wrapped. about the frame, as herein described, terminate aft of the rear spar I0 and are brought together as illustrated in Fig. 4. A metal strip or filler 33 is inserted between the then adjacent edges of the singlev sheet constituting the skin panel .32 and the edges of the skin panel andthe metal strip or spacer 38 are secured together by the rivets 39. The upper and lowerv surfaces of the panels 32 of the skin aligned with the aileron terminate at and are secured to the anges I5 of the rear or aft spar I0 as illustrated in Fig. 5. The upper flange I-.5of the rear spar III coextensive with the Space for the aileron is wider than the flange at the opposite edge of the spar I0 to provide for the mounting of one leaf 4.0 of a piano khinge by which the aileron is mounted .for pivotal movement. In the example here shown, the leafK All is positioned against the under face of the wide flange I5 while the skin edge is' positioned above said Wide flange, the three elements then being secured together by a series of rivets 43. The opposite leaf 42 .of the piano hinge ishinged to the leaf 40, as at y4 I', andcarries the aileron structure as shown in Fig, 5 and as Will be described.

The aileron 'or control surface 44 comprises two or more ribs I 4 each having an outline to dene the profile of the aileron or a movable control surface each provided at its edge with Va lateral, integral flange 45. A single sheet of metal is wrapped around the ribs I4 and is attached to flanges 45 thereof by the rivets 46 passing through theriianges 45 and the metal sheet. The edges of this single sheet of metal areV brought together at the leading edge of the upper surface of the aileron or airfoil to rest upon the leaf 42 of the'hinge where they are secured by the rivets 4'! passing through the hinge leaf 42 and the edges Vof the metal sheet. This airfoil is substantially triangular in cross-section and at its apex 48, which is the trailing edge thereof, the sides are integral one with the other and are brought together to bear upon the filler or spacer 49 to which the sides of the aileron are secured by the rivets or other fastening means 50. The upper and lower surfaces of the aileron or control surfaces are provided with the spaced beads 33 formed similarly to the beads 33 of the panels 32 and are aligned chordwise of the airfoil with the beads 33 of said panels.

The aileron or control surface 44 therefore comprises two or more ribs so wrapped or enveloped by a single metallic sheet that the edges of the sheet terminate one flush against the other at the leading edge of the aileron to rest flush upon the leaf 42 of the piano hinge 4|. In this manner the aileron 44 is hingedly secured to the rearrspar I for any required pivotal movement or adjustment.

What is claimed is:

l. An airfoil structure comprising unitary endsections shaped to dene its profile and close its ends, spars rigidly connected at their ends to said end-sections to form an internal frame, and a skin comprising a single metal sheet bent upon itself to rest ush against the outer edges of said end-sections and spars and having alternate flat and beaded portions, said skin being secured to both the end sections and spars and said beaded portions being interrupted at the leading edge of the airfoil and the breadth of said flat portions being substantially larger than the breadth of said beaded portions.

2. An airfoil structure comprising two sheet metal end ribs formed to define its contour, longitudinal spars interposed between and rigidly secured to said ribs within the limits of said ribs, said ribs and spars each having integral flanges projecting laterally from its edges, a single continuous metal sheet inedially bent to envelope said ribs and spars and terminate at its edges adjoining the trailing edge of said airfoil structure, said sheet having spaced beads formed outwardly therein whereby portions of the sheet bounded by said beads rest flush against flanges of both ribs and spars, and means for securing those portions of said sheet located between said beads and resting flush against the flanges rigidly to the latter.

3. An airfoil comprising two spaced end-sections of sheet metal shaped to define the contour of the airfoil, parallel sheet metal spars spacing and secured to said end-sections and within the limits thereof, and a sheet metal skin bent over and attached to said end-sections thereby forming the leading edge of the airfoil and the upper and lower airfoil surfaces, said skin also being attached to said spars and having its rear edges joined and fastened together to form the trailing edge ofthe airfoil.

4, VA movable airfoil comprising at least two roughly triangular ribs each having a continuous lateral flange at its edge, a skin formed from a single metal sheet enveloping said ribs to rest flush against and be secured to said flanges and having its edges brought together at the leading edge of the airfoil, and a hinge leaf secured to both the edges of the sheet forming the skin of the airfoil.

5. A movable airfoil comprising at least two roughly triangular ribs each having a flange at its edge, a skin formed from a single metal sheet enveloping said ribs and resting flush against and secured to anges with its edges superposed and resting one against the other at the leading edge of the airfoil, and a hinge secured to the superposed edges of the sheet forming the skin of the airfoil.

6. An airfoil comprising an internal frame consisting of two transverse end-sections formed to denne the profile of the airfoil and a longitudinal trailing edge strip, and a rigid skin formed from a single sheet of metal enveloping said endsections and having a rear stiffening bend embracing the strip at the trailing edge of the frame, a lower stiifening bend about the leading edge of the airfoil, the edges of said sheet being brought into relative contact and projected in a direction away from the airfoil to combine to form a reinforced attachment flange, and integral beads formed in the skin between and substantially perpendicular to said bends. n

7. A movable airfoil structure hinged at its leading edge comprising at least two roughly triangular ribs each having a continuous lateral flange at its edge, and a single metal sheet enveloping said ribs to rest flush against and be secured to the said flanges, the edges of the said sheet extending forwardly of and brought together at the upper leading edge of said airfoil to form a supporting ledge for the mounting of the airfoil structure,

8. An airfoil structure comprising two end ribs formed to define its contour, parallel spars eX- tending between and rigidly secured to the said ribs and within the limits thereof, said ribs and spars each having a continuous laterally extending nange at its edges and a series of flanged openings formed in the body portion thereof, and a single metal sheet bent at its midpoint to form the leading edge of the airfoil structure, said sheet resting flush against and being secured to Ysaid ribs and spars and having relatively narrow raised beads formed in each side thereof and eX- tending laterally of the structure at intervals substantially greater than the width of the said beads.

9. An airfoil comprising spaced sheet metal ribs formed to define its contour, three or more spars 'interposed between and rigidly secured to the said ribs, said ribs and spars each having flanges extending laterally from its edges, and a sheet metal skin formed to envelop the afore-mentioned ribs and spars and rigidly secured to the flanges thereof, said skin having transverse Ychannels formed in the inner face thereof spaced one from the other at intervals substantially greater than the width of the said channels.

JOHN GITZ. ALFRED Z. BOYAJIAN.

(References on following page) REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date Haskell Sept. 14, 1920 Black Sept. 22, 1925 Number 

